EP2286045A1

EP2286045A1 - Telescopic mast

Info

Publication number: EP2286045A1
Application number: EP09754084A
Authority: EP
Inventors: Alan John Jenvey; Philip Anthony Nichols
Original assignee: Abacus Holdings Ltd
Current assignee: Abacus Holdings Ltd
Priority date: 2008-05-31
Filing date: 2009-03-23
Publication date: 2011-02-23
Anticipated expiration: 2029-03-23
Also published as: GB0809977D0; RU2010153259A; EP2286045B1; GB2460637A; WO2009144439A1; CN102046902A; AU2009252979A1; GB2460637B

Abstract

A mast for supporting equipment during use, the mast being fixable in a generally upstanding orientation relative to a support surface and comprising: first and second elongate mast sections, the first and the second sections being oriented substantially coaxially; drive means for effecting linear movement of said second section relative to said first section such that the mast is actuable between a first condition in which the second section is retracted relative to said first section, and a second condition, in which the second section is extended; and, transmission means connected in the force path between the drive means and the second mast section and arranged to increase the displacement of the second mast section relative to the first mast section applied by the drive means.

Description

Telescopic Mast

The present invention relates to a mast and more particularly to a mast which is intended in use to support a structure above a mast base section.

Masts are widely used for supporting lighting apparatus above .the ground, such as, for example, at sports stadiums or the like. The height at which flood lighting apparatus can be held above the ground is of significant importance to the effective lighting of an area.

Conventional flood lighting masts, including the head frame on which the lighting equipment is mounted can be as tall as 40-50 metres or more. Accordingly the structural support required at the base of such masts is significant and conventional masts take the form of permanent structures which are erected and fixed in place until they are replaced or else dismantled for maintenance work.

Furthermore, wind loading on the lighting equipment held at such heights above ground level is a significant safety concern. The magnitude of stable wind loading alone can cause a significant moment about the base of the mast. However when this is coupled with the naturally transient nature of wind loading, it becomes difficult to accurately account for maximum peak load and also the effect of potential oscillations in the mast due to gusts or else shedding of the airflow from the edges of the lighting frame.

Such considerations further compound conventional thinking that a mast should be permanently fixed in place with adequate support to withstand the maximum possible loads at all times.

However there is increasing concern over the skyline and the adverse effect that such tall structures are considered to have on the appearance of the surrounding area. Accordingly it is becoming increasingly difficult for organisations to obtain planning permission for the erection of relatively large fixed masts required for effective flood lighting. In meeting such requirements it is often required to provide a mast of sub- optimal height.

In addition it is often necessary to provide a bespoke mast or else the closest height of mast selected from a range of masts to suit the given requirements. The tailoring of a mast design in this manner can add significant cost to the cost of the mast manufacture since masts must be effectively made to order.

Thus it is often necessary for a balance to be struck between the cost of manufacture and installation of a mast; the height at which the lighting equipment can be allowably maintained above the ground; and, the quality of the lighting required for a particular location.

Whilst the application proceeds in relation to lighting masts in particular, it will be appreciated that there are other applications in which tall, load bearing masts are required to support apparatus above the mast base, such as, for example, masts for wind turbines and telecommunications masts. The problems associated with lighting masts may equally be applied to any such other types of mast.

In view of the above problems, there is a need for a mast which offers a reduced negative impact on the appearance of the surrounding area.

According to the present invention, there is provided a mast for supporting equipment during use, the mast being fixable in a generally upstanding orientation relative to a support surface and comprising: first and second elongate mast sections, the first and the second sections being oriented substantially coaxially; drive means for effecting linear movement of said second section relative to said first section such that the mast is actuable between a first condition in which the second section is retracted relative to said first section, and a second condition, in which the second section is extended; and, transmission means connected in the force path between the drive means and the second mast section and arranged to increase the magnitude of the displacement of the second mast section relative to the first mast section applied by the drive means.

In one embodiment the mast comprises a third mast section, which may be elongate in shape and which .may be oriented substantially coaxially with said first section and moveable relative to the first section. The third section may also be linearly moveable relative to the second section. The mast may be telescopic.

Accordingly the mast according to the present invention may be extended and retracted between an at rest condition and an in-use condition or else between different operating heights. This can be is significant benefit since it allows the mast to be extended into a usage condition for required periods of time, without providing an eyesore when not in use.

The present invention may also be particularly advantageous in that a mast may be permanently installed by fixation of the base section relative to a support surface, such as for example the ground. Thus the structural integrity of the mast need not be affected by the raising and lowering of the mast.

This is in contrast to raisable or lowerable mast systems according to the prior art, which typically require a mast of fixed length to be pivoted about a base in order to erect the mast. Such arrangements require a motor/winch drive to pivot the mast into an upright position. The maximum capacity of such winch/motor arrangements has been found to significantly inhibit the size of mast which can be erected according to this method.

Further unexpected advantages may also derive from the present invention. The size of conventional masts can push the boundaries of conventional crane lifting capabilities. However the reduced length of the retracted mast according to the present invention may significantly simplify installation of the mast on site.

Furthermore, the provision of an extending/retracting mast according to the present invention may allow a single mast design to be installed in a number of varying locations. The mast may be simply be extended to a greater or lesser extent during use to account for the varying requirements of different installation sites. In addition, different masts on the same site could be raised to different heights in use if required. Thus the present invention may allow customisation of lighting on a single site in a manner which was not hitherto possible.

The first section may comprise a base or pedestal section of the mast. Alternatively an alternative base or pedestal section may be provided such that any combination of the first and/or second sections may be moveable relative to the base. The base or pedestal section may be hollow and may house the drive means.

The drive means may comprise an hydraulic drive means. In one embodiment, the drive means comprises a linearly moveable drive member and may comprise a piston and cylinder arrangement. The movement of the ram may be a fraction of the required movement of the second or further mast sections. The transmission means may comprise a pulley system. The pulley system may comprise one or more chains having a plurality of links, which may be metallic. The one or more chains may be connected in the force path between the drive means and one or more moveable mast sections. In one embodiment, a pulley system may be connected in the force path between each moveable section of the mast. A ram may drive the lowermost moveable mast section, which may be connected to an adjacent moveable mast section by a pulley system.

A chain may be connected between one end of one mast section and an opposing end of another mast section. The chain may be connected at one end to one mast section and at an opposing end to another mast section. The chain may pass about a pulley wheel. A chain may be connected at one end to a first mast section and may pass over a pulley mounted on a second mast section and may be connected at its second end to a third mast section. The second mast section may be intermediate the first and third mast sections.

Each of the mast sections may be generally tubular or sleeve-like in form such that each mast section may house a further mast section therein. The cross-sectional profile of the or each mast section may have one or more straight edges. Each mast section may have one or more faces which may be flat. Such an arrangement has been found to be beneficial in preventing rotation of the mast sections about the mast axis when compared to mast sections which are generally circular in cross-section. Any or each mast section may be for example rectangular, pentagonal, hexagonal or octagonal.

One or more mast sections may have an opening for passage of the chain therethrough. A pulley may be mounted on the mast section adjacent the opening. One or more mast sections may have attachment formations on an outer wall thereof for attachment of the chain thereto.

One or more alignment members may be provided between adjacent mast sections. The alignment members may comprise friction or buffer members located between one or more walls of adjacent mast sections. The members may be biased so as to urge the mast sections into correct relative or rotational alignment about their shared axis. This can help ensure that the mast sections do not jam due to misalignment. A free end of one mast section may be provided with attachment means for attaching electrical equipment to the mast.

Typically the present invention is applicable to masts which support electrical equipment. The present invention is counter intuitive, since such electrical equipment typically requires permanent electrical connection via cables. The extension and retraction of the mast hampers the use of permanent electrical connections. However the applicant has devised a cable management system suitable to allow a permanent electrical connection to be maintained between the extend and retracted mast conditions.

In one embodiment, one or more cables run through a hollow interior of the first and second mast sections. The or each cable may be held within a cable management structure. The cable management structure may comprise a series of members through which the cable passes, each member being attachable to an adjacent member in a hinge-like arrangement so as to constrain pivoting of adjacent members about only a single axis.

Working embodiments of the present invention are described in further detail below with reference to the accompanying drawings of which:

Figure 1 shows a rear view of a mast according to one embodiment of the present invention;

Figures 2A shows a longitudinal sectional view of a mast according to the present invention in a retracted condition;

Figure 2B shows a three-dimensional view of the mast section shown in figure 2A;

Figures 3A shows a longitudinal sectional view of the mast of figure 2 in an extended condition;

Figure 3B shows a three-dimensional view of the mast section shown in figure 3A; Figure 4 shows a sectional view of additional detail of a mast according to one embodiment of the present invention; and,

Figure 5 shows an example of cable management apparatus for use in conjunction with one embodiment of the present invention.

Figures 1 to 3 show a mast 12 in an upright condition depending from a substantially horizontal support surface 38. All terms used to describe the position and or direction of travel of the mast are relative to the support surface and are not to be construed as being limited to use in conjunction with a horizontal support surface only.

Turning firstly to figure 1 , there is shown a lighting apparatus 10 generally comprising a mast 12 supporting a lighting framework 14. The lighting framework is attached to the upper or head end of the mast 12 and comprises a spinal support member 16 and a plurality of arms 18 extending outwardly therefrom.

Lighting equipment (not shown) is typically mounted on arms 18 for use. In this embodiment, there is provided a connector 20, by which the lighting equipment can be connected or disconnected from a power supply. Electrical cabling is provided within the mast 12 as be described in further detail below. In conventional lighting mast arrangements, the head frame is permanently attached to the mast upon manufacture and the cables are permanently attached to the relevant lighting apparatus.

However the present invention allows for attachment of the head frame 14 to be connected to the mast 12 on site. Thus the plug/socket arrangement 20 on the lighting framework itself allows simple electrical connection and disconnection of the lighting apparatus as required. Power is supplied to lighting equipment mounted on arms 18 via the plug/socket arrangement 20.

The mast 12 comprises a base section 22 and a plurality of elongate mast sections 24 depending therefrom. The plurality of mast sections 24 comprise a first 26, a second 28, a third 30 and a fourth 32 mast section. Each mast section takes the form of a substantially hollow tubular formation, with the first section having the greatest lateral or width dimension such that it can house the second, third and fourth mast sections therein. The fourth mast section 32 is mounted within the third mast section which is mounted within the second mast section, which is in turn mounted within the first mast section in a concentric arrangement.

Each of the first, second and third mast sections has alignment formations comprising friction members 31 mounted therein. The friction members 31 are arranged to provide frictional contact between the mast section in which the pads are mounted and an adjacent mast section. In this embodiment, the pads contact the radially inner adjacent mast section. Such alignment formations may be provided at an or any combination of the upper, mid or lower region of the mast sections.

The first mast section 26 has at its lower end a circumferential mounting flange 33 which faces a similarly shaped mounting flange 34 on the base section 22. Bolts are passed through the opposing mounting flanges when they are in abutment so as to secure the base 22 and the first mast section in an end to end engagement.

The base 22 may have an opening 36 in order to provide access to its hollow interior. The base section is fixed in an upstanding orientation to a support surface 38. It will be understood by the person skilled in the art that an additional support structure or foundation for the mast may be provided below the level of the support surface 38 and may be sunk below ground level.

The fourth mast section 32 being the uppermost mast section when the mast is oriented as shown in figure 1 has a flange formation at its free end for attachment of the head frame 14 thereto. The spinal portion 16 of the head frame may have a corresponding opposing flange portion at its lower end.

Turning now to figure 2, there are shown longitudinal sectional views of the mast 12 taken through its centreline 40. The base section 22 of the mast has been removed. The mast 12 is in a retracted condition such that each of the mast sections 28, 30 and 32 extend into the interior of the mast section 26. In this condition a minor portion of each of mast sections 28, 30 and 32 protrudes from an upper end of the section 26. A majority of the length of each of those sections is enclosed within section 26.

Each of sections 28, 30 and 32 are arranged to be movable relative to section 26 when the mast is converted to its extended or in-use condition as will be described below. Sections 28, 30 and 32 may be referred to hereinafter as the movable or moving mast sections.

The mounting flange formation 42 of the uppermost or fourth mast section 32 is shown in figure 2 and comprises an end plate of greater diameter than that of the tubular portion of mast section 32. The flange 42 has openings therein for bolting the head frame 14 thereto.

The other mast sections, namely the first 26, second 28 and third 30 sections, each have a collar formation 44 at the upper end thereof. The collar formations 44 protrude outwardly of the wall of the corresponding section and provides an abutment against which the collar 44 of the adjacent mast section can rest in the retracted condition. Each collar portion thus serves as a stop to ensure that the moveable mast sections are not completely retracted within the adjacent mast section.

In this embodiment, the collar formations each comprise a pair of spaced circumferential lip or rim formations which depend outwardly from the tubular body of each mast section.

As can be seen in figure 2, the mast sections are not circular in cross section. The mast sections each have a plurality of substantially flat side walls and, in this embodiment, the mast sections are octagonal in cross section. The non-circular nature of the side walls helps to provide torsional stability of the mast about its centreline and resists twisting such as, for example, as a result of wind loading. It is envisaged that other polygonal cross-sectional profiles or else an elliptical section may provide suitable alternatives for this purpose.

A drive means in the form of a hydraulic ram 46 is provided within the mast 12. In this embodiment, the ram 46 is mounted in the interior space of the first mast section 26. The first mast section is rigidly attached to the base section and not moved during extension or retraction of the mast.

The ram 46 comprises a piston 48 and cylinder 50 arrangement. The cylinder comprises an internal cavity 52, within which the piston 48 is seated. Fluid is applied under pressure to the internal cavity 52 to cause relative movement between the piston and cylinder. The ram 46 is anchored by a supporting rod formation 54 which passes into the base section 22. In this embodiment, the head of the piston 48 is attached to the base and the cylinder 50 is moveable relative thereto in use. The head of the piston is thus attached to the rod formation 54.

The cylinder 50 has connection formations in the form of opposing pins or lugs 56 which protrude outwardly of the cylinder body at its lowest end. The lugs 58 are received in correspondingly shaped openings 58 within an internal support member 60 of the second mast section 28. The lugs 58 and internal support member 60 are load bearing in that they allow transfer of force from the ram 46 to the second cylinder.

The internal support member 60 comprises an inwardly extending cross member which depends from the wall of the second mast section. The support member may span between opposing side walls of the second mast section. The support member may comprise opposing plate formations, between which the ram is mounted.

A pulley system is also provided for the transfer of force to the third and fourth mast sections during use. The pulley system allows the ram to indirectly actuate the third and fourth mast sections during operation as will be described in further detail below.

The pulley system comprises a first linked metal chain 62 which is connected at one end to the upper end of the first mast section 26. The first chain 62 is connected to the collar 44 of the first mast section by a bolt fastener. The first chain passes from the first mast section over a pulley 64 mounted at an upper end of the second mast section and terminates at a fastening 66 on the wall of the third mast section 30. The fastening 66 is provided part way along the length of the third mast section and typically towards its lower end (i.e. spaced from the upper end of the adjacent mast section). The chain 62 is connected to the fastening 66 by a bolt (not shown).

The first chain 62 provides a force path between the first and third mast sections which is actuable by movement of the second mast section.

A second chain 68 is connected at one end to the upper end of the second mast section.

The second chain 68 is connected to the collar 44 of the second mast section by a bolt fastener. The second chain passes from the second mast section over a pulley 70 mounted at an upper end of the third mast section 30 and terminates at a fastening 72 on the wall of the fourth mast section 32. The fastening 72 is provided part way along the length of the fourth mast section and typically towards its lower end (i.e. spaced from the upper end of the adjacent mast section). The chain 68 is connected to the fastening 72 by a bolt (not shown).

The second chain 68 provides a force path between the second and fourth mast sections which is actuable by movement the third mast section.

Whilst only a first 62 and a second chain 68 are described for simplicity, it will be appreciated that additional chain and pulley systems may be used in parallel with the first and second chains for additional strength. Such an arrangement is shown in figures 2 and 3, in which an additional first chain 74 is provided on an opposing side of the mast in parallel with the first chain 62 which passes over an additional pulley mounted to the second mast section and having connections to the mast sections as described above. An additional second chain 76 and pulley system is also provided in parallel with the second chain 68 and mounted on the opposing side of the mast.

Electrical cables 78 depend from the wall of the first mast section 26. The cable 78 passes beneath the lowermost ends of the moveable mast sections and is attached to the uppermost or fourth mast section. The cable may pass through an opening 80 in the end plate 42 of the fourth mast section for connection to the head frame 14 via the plug and socket arrangement 20 shown in figure 1. Thus the cable 78 is fixedly attached at each end to the first and fourth mast sections but hangs free in its mid section. The mid section may be provided with a cable management structure to control the freedom of movement of the cable within the mast.

The cable 78 may be connected to one or more power lines within the mast base or else may pass outside the mast through an opening in the wall thereof for connection to power lines outside of the mast.

Turning now to figure 3, the mast is shown in its extended condition, wherein the length of the mast is substantially greater than that shown in figure 2. However it will be appreciated that the mast is not a maximum extension. In order to actuate the mast 12 between its retracted and extended conditions, pressure is applied to the cylinder chamber 52 of the ram 46. The cylinder is forced away from piston 48 and the force exerted by the pressurised fluid in the chamber 52 is transmitted to the second mast section 28 via the lugs 56 and cross member 60. Thus the second mast section 26 is actuated by the ram 46 and moves in unison therewith relative the first mast section.

The first mast section provides a rigid sleeve, through which force from the drive means can be transmitted to the other moveable mast sections via the pulley system. As the second mast section moves relative to the first mast section, a tension is applied to first chain 62 via pulley 64 which moves in unison with the second mast section 28. The first end of the first chain 62 is attached to the first mast section which is fixed in position, whereas the second end of the first chain is attached to the third mast section, which is moveable. The movement of the pulley 64 with the second mast section 28 causes the first chain 62 to ride upward on the pulley 64, resulting in a corresponding movement of the third mast section 30.

Similarly, the movement of the third mast section 30 and the pulley 70 mounted thereon, applies a tension in the second chain 68 which rides up the pulley 70. This results in movement of the fourth mast section 32 in unison with the third 30 and second 28 mast sections.

Thus the possible extension of the mast 12 far exceeds the maximum extension of the ram 46. In this example, the mast may be extended by a multiple of the movement of the ram based upon the number of moveable mast sections present. For example, a mast having three moveable sections may be extend by three times the extension of the ram.

The relative width and length dimension of the masts shown in figures 1 to 4 are not intended to be to scale in order to clearly show the important technical features of the present invention.

By way of example only, a working mast according to the present invention may have a maximum length in the region of 20 to 50m and may have a maximum diameter in the region of 0.6 to 2m, excluding the head frame. The load to be supported by the mast for a laden head frame may be, by way of example, in the region of 3 tonnes. The length of travel of the piston/cylinder arrangement may be in the region of 5-8m and the total extension of the mast may be in the region of 15 to 24m or more dependent on the ram specification, the number of mast sections and pulley system used.

Further details of the lower end of the mast 12 are shown in figure 4. It can be seen that the first mast section is provided with reinforcing spline formations 82 running along the outer edge of the walls thereof. Similar formations may be provided along the other mast sections.

The lower end of the ram 46 is embedded within the interior of base section 22 and comprises a port for application of pressure thereto.

In addition, the alignment formations are shown in further detail. One or more alignment formations may be provided in a side wall of a mast section. In the embodiment shown, alignment formations are provided in opposing walls of each mast section, typically in each moveable mast section. More specifically, alignment members are provided in four of the eight faces of each of the moveable mast sections.

The relevant faces of the mast sections are provided with an aperture having a circumferential wall 84 thereabout. The aperture and wall 84 define an open-ended recess in which is received a friction member 86. The friction member 86 is formed of a body of resilient material such as a rubber or the like which is pressed against the corresponding wall of the adjacent mast section. Retaining members 88 are used to hold the friction member within its recess and may take the form of a pair of retaining formations which span the recess opening in the form a cross. The degree to which the friction members protrude from the recess can be adjusted to ensure a close fit between adjacent mast sections.

Friction members mounted at the mid or the lower regions of each mast section may be oriented to press against the inner face of the radially outer adjacent mast section, whereas friction members mounted at an upper end of each mast section may be oriented to press against the outer surface of the radially inner adjacent mast section. Any or every mast section may have a plurality of friction members mounted towards each end thereof and/or along its length. In one embodiment, the mast can be retracted from its extended condition under gravity. The weight of the mast and the structure attached at its head end may serve to retract the mast as pressure is released in a controlled manner from the cylinder chamber 52.

Whilst this does represent one operable embodiment of the present invention, it will be appreciated that any interruption to the retraction of the mast, such as by way of jamming or snagging of the chains or else misalignment of the mast sections, could pose a significant problem due to the weight of the mast and head structure. Accordingly it is proposed to provide an active retraction system which drives the system between an extended and retracted condition.

In such an active retraction system, a further pulley system may be employed which opposes the pulley system shown in figures 2 and 3. Similar to the pulley system shown in figures 2 and 3, the retraction pulley system may employ a pair of chains located on opposing sides of each section. Such retraction chains may be interposed between the pairs of chains shown in figures 2 and 3. The retracting pulley system will be driven against the pressure applied to the cylinder chamber 52. A further drive means in the form of a piston/cylinder or else a winch/motor arrangement may be required to drive the retraction mechanism. The pressure in the cylinder 52 will typically be released under control as the retraction mechanism is operated so as to maintain a tension in chains 62, 68, 74 and 76.

Figure 5 shows details of a cable management structure which may be used in conjunction with the present invention. During extension of the mast, the upper end of cable 78 travels in unison with the fourth mast section to which it is attached. This causes slack in the cable to be taken up. It will be appreciated that the length of the slack in the cable is equal to or greater than the maximum length of extension of the mast 12.

The cable management structure 89 as shown in figure 5, comprises a plurality of open ended housing members 90, each having opposing side wall formations 92. The side walls 92 are spaced by top and bottom members 94 which extend between the side walls so as to define an at least partial enclosure for the cable. The side walls of the housing members are provided with connection formations in the form of lugs and correspondingly shaped apertures such that the lugs of one housing member can be inserted into the apertures of an adjacent housing member. In this manner a plurality of housing members can be attached in an end to end arrangement so as to create a length of housing members in the form of a one-dimensional array. Each member in the array is hinged relative to the adjacent members in the array such that the cable management structure is multiply pivotable about axes of rotation transverse to the length of the cable.

The formation of the cable management structure provides lateral stability and hinders deformation of the cable about any axis other than the axes of rotation permitted by the lug-and-aperture arrangement of the housing members. Thus the length of cable which is left slack when the telescopic mast is retracted falls in a predictable manner and does not form coils or randomly oriented loops which may snag and resists extension of the mast.

Whilst the above description relates to a mast having a fixed first section and three moveable sections, it will be appreciated that any number of moveable sections may be used to meet the necessary mast extension characteristics. The minimum requirement is a fixed base section and a single moveable section. For such an arrangement, the ram may not be directly to the moveable mast section but may instead be connected thereto via a pulley system in order to multiply the degree of travel of the moveable mast section relative to the movement of the ram.

For masts having multiple moveable mast sections, the first mast section preferably shares a one-to-one movement ratio with the ram, which movement is used to actuate further mast sections via a pulley system.

The telescopic mast system described above is not limited to use with lighting apparatus and may be applied to, for example, wind turbines or the like, wherein the uppermost portion of the mast may be provided with suitable attachment formations for fixation of a wind turbine thereto. Similarly a retracting mast of this kind may be used for telecommunications applications such as for a telecommunication base station which may support telecommunications equipment for transmission and/or receipt of signals.

Claims

Claims:

1. A mast for supporting equipment during use, the mast being fixable in a generally upstanding orientation relative to a support surface and comprising: first and second elongate mast sections, the first and the second sections being oriented substantially coaxially; drive means for effecting linear movement of said second section relative to said first section such that the mast is actuable between a first condition in which the second section is retracted relative to said first section, and a second condition, in which the second section is extended; and, transmission means connected in the force path between the drive means and the second mast section and arranged to increase the displacement of the second mast section relative to the first mast section applied by the drive means.

2. A mast according to claim 1 , wherein the mast is telescopic and the first and second mast sections are arranged concentrically.

3. A mast according to claim 1 or claim 2, wherein the first mast section is substantially tubular in form having a width dimension greater than the width of the second mast section such that the second mast section is locatable within the first mast section.

4. A mast according to claim 3, wherein the second mast section comprises a collar of increased width at one end thereof, said collar providing an abutment for contacting a corresponding end of the first collar section in the retracted condition.

5. A mast according to any preceding claim, comprising a third mast section, which is elongate in shape and which is oriented substantially coaxially with said first section and linearly moveable relative to the first section.

6. A mast according to any preceding claim, wherein the drive means comprises a piston and cylinder arrangement arranged to be driven by fluid pressure.

7. A mast according to any preceding claim, wherein the first section comprises a base section arranged to be rigidly fixed in position relative to the support surface, within which the drive means is located.

8. A mast according to any one of claims 1 to 6, further comprising a base section arranged to be rigidly fixed in position relative to said support surface, the first and second mast sections arranged to be linearly moveable relative to said base section.

9. A mast according to claim 8, wherein the drive means actuates the first section directly between the retracted and extended conditions, and the movement of said first section causes concurrent movement of the second section via said transmission means.

10. A mast according to any preceding claim, wherein the transmission means comprises a pulley system.

11. A mast according to claim 10, wherein the pulley system comprises a chain connected between a base mast section and the second mast section, the chain passing about an upper portion of said first mast section such that relative movement between the first section and the base section causes actuation of the second mast section via said chain.

12. A mast according to claim 10 or 11 , wherein one or more mast sections has a pulley mounted thereto for passage of a force transmission chain thereabout.

13. A mast according to any one of the preceding claims, wherein the or each mast section is polygonal in cross section such that the or each mast section has a plurality of adjoining exterior faces.

14. A mast according to any one of the preceding claims, comprising one or more alignment members provided between adjacent mast sections, the alignment member being located between corresponding walls of the first and second mast sections such that the alignment member is in compression and serves to maintain a spacing between said walls of the first and second members.

15. A mast according to claim 14, wherein alignment members are provided on circumferentially adjacent or spaced side walls of the first and/or second mast section.

16. A mast according to any one of the preceding claims, wherein one or more power cables run through a hollow interior of the first and second mast sections, the cable being constrained within a cable retaining structure having a series of adjoining members through which the cable passes, each member being attachable to an adjacent member in a hinge-like arrangement so as to constrain the freedom of movement available to said cable.

17. A mast substantially as hereinbefore described with reference to the accompanying drawings.